RBP4 and type 2 diabetes mellitus: Despite mechanistic links, the epidemiological observational evidence to date is yet inconclusive and partly sparse.9 Although retinol levels have been reported to be inversely and positively associated with CVD risk, there is a lack of epidemiological studies investigating its association with T2D risk.9,10 Circulating RBP4 levels were mostly found to be positively associated with CVD and T2D risk.